Add reverseproxy auth for API back with default disabled (#26703)

This feature was removed by #22219 to avoid possible CSRF attack.

This PR takes reverseproxy auth for API back but with default disabled.

To prevent possbile CSRF attack, the responsibility will be the
reverseproxy but not Gitea itself.

For those want to enable this `ENABLE_REVERSE_PROXY_AUTHENTICATION_API`,
they should know what they are doing.

---------

Co-authored-by: Giteabot <teabot@gitea.io>

custom/conf/app.example.ini

@@ -759,6 +759,8 @@ LEVEL = Info
 ;;
 ;; More detail: https://github.com/gogits/gogs/issues/165
 ;ENABLE_REVERSE_PROXY_AUTHENTICATION = false
+; Enable this to allow reverse proxy authentication for API requests, the reverse proxy is responsible for ensuring that no CSRF is possible.
+;ENABLE_REVERSE_PROXY_AUTHENTICATION_API = false
 ;ENABLE_REVERSE_PROXY_AUTO_REGISTRATION = false
 ;ENABLE_REVERSE_PROXY_EMAIL = false
 ;ENABLE_REVERSE_PROXY_FULL_NAME = false

docs/content/administration/config-cheat-sheet.en-us.md

@@ -621,7 +621,8 @@ And the following unique queues:
    BASIC and the user's password. Please note if you disable this you will not be able to access the
    tokens API endpoints using a password. Further, this only disables BASIC authentication using the
    password - not tokens or OAuth Basic.
-- `ENABLE_REVERSE_PROXY_AUTHENTICATION`: **false**: Enable this to allow reverse proxy authentication.
+- `ENABLE_REVERSE_PROXY_AUTHENTICATION`: **false**: Enable this to allow reverse proxy authentication for web requests
+- `ENABLE_REVERSE_PROXY_AUTHENTICATION_API`: **false**: Enable this to allow reverse proxy authentication for API requests, the reverse proxy is responsible for ensuring that no CSRF is possible.
 - `ENABLE_REVERSE_PROXY_AUTO_REGISTRATION`: **false**: Enable this to allow auto-registration
    for reverse authentication.
 - `ENABLE_REVERSE_PROXY_EMAIL`: **false**: Enable this to allow to auto-registration with a

modules/setting/service.go

@@ -46,6 +46,7 @@ var Service = struct {
 	EnableNotifyMail                        bool
 	EnableBasicAuth                         bool
 	EnableReverseProxyAuth                  bool
+	EnableReverseProxyAuthAPI               bool
 	EnableReverseProxyAutoRegister          bool
 	EnableReverseProxyEmail                 bool
 	EnableReverseProxyFullName              bool
@@ -157,6 +158,7 @@ func loadServiceFrom(rootCfg ConfigProvider) {
 	Service.RequireSignInView = sec.Key("REQUIRE_SIGNIN_VIEW").MustBool()
 	Service.EnableBasicAuth = sec.Key("ENABLE_BASIC_AUTHENTICATION").MustBool(true)
 	Service.EnableReverseProxyAuth = sec.Key("ENABLE_REVERSE_PROXY_AUTHENTICATION").MustBool()
+	Service.EnableReverseProxyAuthAPI = sec.Key("ENABLE_REVERSE_PROXY_AUTHENTICATION_API").MustBool()
 	Service.EnableReverseProxyAutoRegister = sec.Key("ENABLE_REVERSE_PROXY_AUTO_REGISTRATION").MustBool()
 	Service.EnableReverseProxyEmail = sec.Key("ENABLE_REVERSE_PROXY_EMAIL").MustBool()
 	Service.EnableReverseProxyFullName = sec.Key("ENABLE_REVERSE_PROXY_FULL_NAME").MustBool()

routers/api/v1/api.go

@@ -333,8 +333,11 @@ func reqExploreSignIn() func(ctx *context.APIContext) {
 	}
 }
 
-func reqBasicAuth() func(ctx *context.APIContext) {
+func reqBasicOrRevProxyAuth() func(ctx *context.APIContext) {
 	return func(ctx *context.APIContext) {
+		if ctx.IsSigned && setting.Service.EnableReverseProxyAuthAPI && ctx.Data["AuthedMethod"].(string) == auth.ReverseProxyMethodName {
+			return
+		}
 		if !ctx.IsBasicAuth {
 			ctx.Error(http.StatusUnauthorized, "reqBasicAuth", "auth required")
 			return
@@ -698,6 +701,9 @@ func buildAuthGroup() *auth.Group {
 		&auth.HTTPSign{},
 		&auth.Basic{}, // FIXME: this should be removed once we don't allow basic auth in API
 	)
+	if setting.Service.EnableReverseProxyAuthAPI {
+		group.Add(&auth.ReverseProxy{})
+	}
 	specialAdd(group)
 
 	return group
@@ -800,7 +806,7 @@ func Routes() *web.Route {
 					m.Combo("").Get(user.ListAccessTokens).
 						Post(bind(api.CreateAccessTokenOption{}), reqToken(), user.CreateAccessToken)
 					m.Combo("/{id}").Delete(reqToken(), user.DeleteAccessToken)
-				}, reqBasicAuth())
+				}, reqBasicOrRevProxyAuth())
 
 				m.Get("/activities/feeds", user.ListUserActivityFeeds)
 			}, context_service.UserAssignmentAPI())